Re: [Xen-devel] [PATCH v3 ]libxl: allow to set more than 31 vcpus

[Dario Faggioli <raistlin@xxxxxxxx>]

On Fri, 2012-06-01 at 09:58 +0100, Ian Campbell wrote: 
> > > And, in future, there are some cases may not need to allocate max size 
> > > cpumap too
> > > So it's better to extend the current interface.
> > > 
> > Well, maybe... Who knows what future reserves ?!? :-D
> > 
> > Anyway, although I see your point, I really really dislike the new
> > parameter in libxl_cpumap_alloc(),
> 
> What about it do you dislike? The special meaning of 0 or its existence
> at all?
> 
It's pretty much all about its existence, given the fact it is _always_
0 apart from one single case, where it could well be zero as well. :-)
It's just I find it uncomfortable to have it, but of course I could live
with it if it buys something. It's the latter I'm not sure I see...

> > but of course it is not something up
> > to me to decide, neither it is something I'd loose some sleep for. :-P
> 
> You could give vcpus > pcpus (dumb, but e.g. for debugging) and in that
> case the existing libxl_cpumap_alloc behaviour (which sizes based on the
> # of phys cpus) is incorrect. 
>
Mmm... Maybe this is still related to the fact that on all the test
boxes I've used, libxl_get_max_cpus() returns something higher than the
actual physical CPU count of those boxes themselves, but I just created
an 18 VCPUs VM on my 16 PCPUs test machine... I take the above like you
can't, can you?

Maybe it is that *_max_cpus() logic that needs some attention? :-O

> I suggested that rather than having
> libxl_cpumap_alloc_size() we just combine this with the existing fn with
> a new parameter.
> 
Yeah, I checked that in the archives, and that's not the issue for me.
If the we decide we want the thing, I'm fine with both the 'add new' and
'modify the existing' approaches. 

Thanks and Regards,
Dario
|
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://retis.sssup.it/people/faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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